In this worksheet, we will learn how to increase and decrease numbers by a given percentage using a calculator.

__Methods and Examples__

A whole number or quantity is 100%.

Increasing a number by 10% gives 100% + 10% = 110% of the number or 1.1 × the number.

So 25cm increased by 10% is **1.1 **× 25 = 27.5 cm.

Decreasing a number by 15% gives 100% - 15% = 85% of the number or 0.85 × the number.

So 25cm decreased by 15% is **0.85 **× 25 = 21.25 cm.